Universiteit Leiden

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Students are programming with qubits

Students of the Leiden University master Computer Science are the first students in the world that have been educated in programming with a quantum computer. ‘With this system, it is finally possible to solve complex real-life problems of society.‘

Zeros and ones as well

‘Quantum physics is actually not that difficult’, says teacher of the course Florian Neukart. ‘Computer scientists quickly learned enough about it to be able to exert quantum effects for computation. If we represent a quantum bit in terms of electron spin, then spin-up would be state 0 and spin-down state 1. Those zeros and ones we already know from classical computers, but one advantage of a quantum computer is that every bit – a qubit - can take up 0 and 1 at the same time. This is the reason a quantum computer can be more powerful than a classical computer. In a classical computer, it is always 0 or 1.’

Lots of calculations at a time

So the number of calculations a quantum computer can perform at a certain moment, is way bigger than in a classical computer. Neukart: ‘We have been working with the quantum computer of the company D-Wave. As of now, they have 2000 qubits in place. It makes it possible to do 2 to the power of 2000 function evaluations at any moment. A classical computer would have to calculate all possible configurations sequentially, which may be impossible in finite time.’

Solve real-life problems

‘The great advantage of being able to do so many calculations at the same time, is that you can finally perform the complex tasks that you come across in society. Regarding the D-Wave system, the students have worked on questions such as image classification. As the set-up of the course was more practical than the old theoretical lectures of quantum computing, the students got a better understanding of how you can solve real-life problems with a quantum computer.'

‘It is going fast in this profession’

The German computer scientist Florian Neukart is working at Volkswagen in San Francisco. Once a year he gives the course Quantum computer science to master students of Computer Science at Leiden University. ‘This is the first time that I am using the software libraries for accessing the local solvers provided by D-Wave this way and that I have the students program something on it. Up to last year, I was not 100% convinced that one could solve our optimization problems with it. But after having gained some hand on experience with the system, I changed my mind. That is how fast it is going in this profession.’

Few in the field

In his course, Neukart is using the local solver: a local system for solving optimisation problems, which performs the same tasks as does the quantum computer. 'But slower, of course. D-Wave has given us permission to use their simulator. You could call that extraordinary. One D-Wave system costs 15 million dollars. Outside D-Wave’s lab there are only three installed in the field. One of those, for example, is at the Quantum Artificial Intelligence Lab run by Google, NASA and USRA. At Volkswagen, we are submitting our data through the internet and are paying by the hour. But the internet is an open system, so we don’t want to use real data of our customers.’ Laughing: ‘Indeed, I would love to have a D-Wave’.